The purpose of the proposed research is to further study the mechanism of action of uricosuric drugs which are used in the treatment of gouty arthritis. Since the precise mechanism of action of uricosuric drugs is currently unknown, the development of new and better compounds is substantially hindered. This laboratory is developing biochemically oriented procedures directed toward the elucidation of the mechanisms of uricosuric action on a molecular level. To that end, the research will examine transport of uric acid in isolated renal plasma membranes from the rabbit. Procedures will be developed to isolate membranes from both basal-lateral and brush border aspects of the renal tubule using the techniques of differential and density-gradient centrifugation and free-flow electrophoresis. Membranes will be identified by their contents of established marker enzymes (Na ion plus K ion -ATPase identifies basal-lateral and trehalase indentifies brush border membranes) and by microscopical techniques. Initial experiments will examine the characteristics of uric acid transport in the isolated membranes using a rapid Millipore filtration technique. Subsequent research will examine the mechanisms by which drugs alter the unidirectional flux of uric acid across the basal lateral and brush border membranes with emphasis on determining specificity of drug action, kinetics of inhibitory effects, and drug induced alterations in physical properties of the isolated membranes. In addition, experiments will be conducted to isolate and characterize a transport system for uric acid and other organic acids using reconstitution of uric acid transport in artificial proteoliposomes as an assay for recovery of transport related membrane components.